Silicon carbide (SiC) is considered as capable of achieving high-temperature performance, high-frequency performance, voltage resistance, and environment resistance each of which could not be achieved by conventional semiconductor materials, such as silicon (Si) and gallium arsenide (GaAs), and is therefore expected as a semiconductor material for next-generation power devices and high-frequency devices.
Patent Literature 1 proposes to use a tantalum container having a tantalum carbide layer formed on the surface thereof as a chamber in thermally annealing the surface of a single crystal silicon carbide substrate and in growing a single crystal of silicon carbide on a single crystal silicon carbide substrate. The literature reports that by containing a single crystal silicon carbide substrate in a tantalum container having a tantalum carbide layer on the surface thereof and thermally annealing its surface or growing a silicon carbide single crystal on its surface, a single crystal silicon carbide substrate or a silicon carbide single crystal layer can be formed in which its surface is planarized and has less defects.
Patent Literatures 2 and 3 propose a carburizing method in which Ta2O5 as a naturally oxidized film existing on the surface of tantalum or a tantalum alloy is removed by sublimation and carbon is then allowed to penetrate the surface to form tantalum carbide on the surface.
However, the above methods present a problem in that in carburizing the workpiece in the chamber by reducing the pressure inside the chamber and heating the interior of the chamber, the gas in the chamber is exhausted by an evacuating pump to produce a gas flow in the chamber and carbon from the carbon source moves along the gas flow, so that the surface of the tantalum container cannot be uniformly carburized.
Furthermore, no specific proposal has been heretofore given of a method for uniformly carburizing the surface of a tantalum container.